Abstract

Background

This study was performed to examine whether patients with type 2 diabetes have cognitive
deficits associated with the prefrontal cortex (PFC).

Methods

Twenty-seven middle-aged patients with newly diagnosed type 2 diabetes and 27 healthy
controls underwent physical measurements and neuropsychological tasks. Response inhibition,
reward prediction, and executive function were assessed by the Go/NoGo task, the reversal
and extinction tasks, and the Wisconsin Card Sorting Test (WCST). To examine the interactions
of being overweight with diabetes on cognitive performance, performance data were
analysed by two-way ANCOVA with diabetes and overweight as factors and age as a covariate.

Results

Patients with type 2 diabetes showed significantly decreased response inhibition in
the Go/NoGo task (discriminability index: P = 0.001). There was an interaction of being overweight with diabetes on reaction time
in the Go trials of the Go/NoGo task (P = 0.009). Being overweight was related to retained responses to the presentiment of
reward in the extinction task (P = 0.029). The four groups showed normal cognitive performance in the WCST.

Conclusions

Our results showed that middle-aged, newly diagnosed and medication-free patients
with type 2 diabetes have a particular neuropsychological deficit in inhibitory control
of impulsive response, which is an independent effect of diabetes apart from being
overweight.